The movement of nutrients, wastes, electrolytes, and water through the human intestines depends on the proper balance of absorption and secretion of water and electrolytes by the intestinal epithelium. Various pathogens, physical conditions and drugs can affect this balance or affect intestinal motility which can result in constipation. Laxatives can be used to treat constipation by promoting defecation. In addition, laxatives are useful for bowel clearance before radiological examination, colonoscopy, endoscopic examination, surgery or childbirth.
There are three basic mechanisms of laxative action. The first mechanism is the retention of fluid in colonic contents by the hydrophilic or osmotic properties of the laxative compositions. The second mechanism is a decrease in the absorption of water and NaCl by acting directly or indirectly on the colonic mucosa. The third mechanism of action is an increase in the intestinal motility, which causes decreased absorption of water and salt due to the increased transit time.
There are several different types of laxatives including dietary fiber and bulk-forming laxatives, stimulant laxatives, and saline and osmotic laxatives. Commonly used laxative products include castor oil, magnesium citrate, bisacodyl, PEG-electrolyte lavage and sodium phosphate. PEG-Lavage and sodium phosphate are the most commonly used products for colon cleansing prior to endoscopic examination.
The present sodium phosphate composition is an oral saline laxative and bowel cleanser. Saline laxatives are poorly and slowly absorbed and act by their osmotic properties in the luminal fluid. A commonly used oral saline laxative is "FLEET PHOSPHO-SODA" (21.6 g monobasic sodium phosphate and 8.1 g dibasic sodium phosphate in 45 ml of a stable buffered aqueous solution). This product has been found by most patients to have an unpleasant taste despite the addition of flavorings. In addition, some patients become nauseated and are affected by the slight electrolyte imbalance from using this product. In view of these problems, the object of the present invention is to provide a sodium phosphate bowel cleansing composition which has a pleasant taste and preferably binds ions to reduce the amount of electrolyte shift caused by the absorption of ions from the composition.
Though powdered pharmaceuticals may have been coated to mask taste in the past, the coating of sodium phosphate powders or crystals presents unique difficulties in that these compounds are highly ionic inorganic salts which are administered in larger amounts than most pharmaceuticals and require prolonged contact with water in a suspension. In view of this, the coatings which are used must have pores which are small enough to prevent the migration of ions through the coating and the coatings must be usable in amounts sufficient to coat large quantities of powder without adversely affecting the desired pharmacological effect. The present invention solves these problems allowing the production of a sodium phosphate bowel cleansing composition which has improved taste and retains the desired pharmacological effect.